Add samsung specific changes

mm/sec_mm/lowfile_detect.c

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * sec_mm/
+ *
+ * Copyright (C) 2020 Samsung Electronics
+ *
+ */
+
+#include <linux/mm.h>
+#include <linux/ratelimit.h>
+#include <linux/sec_mm.h>
+
+#define MIN_FILE_SIZE_HIGH	300
+#define MIN_FILE_SIZE_LOW	200
+#define MIN_FILE_SIZE_THR_GB	3
+
+static unsigned long min_file;
+
+static unsigned long lowfile_count(struct shrinker *s,
+				struct shrink_control *sc)
+{
+	unsigned long inactive_file, active_file, file;
+	static DEFINE_RATELIMIT_STATE(mm_debug_rs, 10 * HZ, 1);
+
+	inactive_file = global_node_page_state(NR_INACTIVE_FILE);
+	active_file = global_node_page_state(NR_ACTIVE_FILE);
+	file = inactive_file + active_file;
+	if (file < min_file && __ratelimit(&mm_debug_rs)) {
+		pr_info("low file detected : %lukB < %luKB\n", K(file),
+			K(min_file));
+		show_mem();
+	}
+	return 0; /* return 0 not to call to scan_objects */
+}
+
+static struct shrinker mm_debug_shrinker = {
+	.count_objects = lowfile_count,
+};
+
+void init_lowfile_detect(void)
+{
+	if (totalram_pages() > GB_TO_PAGES(MIN_FILE_SIZE_THR_GB))
+		min_file = MB_TO_PAGES(MIN_FILE_SIZE_HIGH);
+	else
+		min_file = MB_TO_PAGES(MIN_FILE_SIZE_LOW);
+
+	register_shrinker(&mm_debug_shrinker, "mm_debug_shrinker");
+}
+
+void exit_lowfile_detect(void)
+{
+	unregister_shrinker(&mm_debug_shrinker);
+}